There is no fuse.
What is wrong is that by replacing the circuit cards, you have to remove the retaining nut on the gauges. Underneath the circuit card is a cardboard insulator that slips over the two posts. There's enough slop in the gauge fitment into the cluster itself that it is EXTREMELY easy to have one of the posts contact the metal housing, particularly since you cannot see what is going on beneath the insulating pads, the circuit cards, and the retaining nuts. Once one of the posts contacts metal, all three gauges are essentially short-circuited.
How to test? Measure the resistance from each post to ground: you should see kilo-ohms at worst. If you see 1 ohm or 13-14 ohms, then that post is grounded (1 ohm) or the other post is grounded (13-14 ohms). The input power to each of the gauges (oil, water, fuel) is common to all 3 gauges. This test is also essential for the ammeter; if any of the ammeter posts are grounded, you will quickly have a dead short to battery and a fire and smoke will result in seconds. If you see low resistance, loosen the retaining nuts and wiggle the gauge such that the posts are not contacting the side of the slot allowing the posts to stick through.